The NASA Ames Research Center Modular Supercomputing Facility is highly efficient, both in terms of electricity and water use. The facility isn't air conditioned. The chips are water cooled, and the inlet water temperature is pretty high I believe - I think it's 90 degrees Fahrenheit.

https://www.nasa.gov/centers-and-facilities/ames/doing-more-...

https://www.nas.nasa.gov/assets/nas/pdf/ModularSupercomputin...